1. Field of the Invention:
This invention relates to an oxygenator to be used for external circulation. More particularly, this invention relates to an oxygenator improved to delay amply the loss of gas-exchange capacity by aging.
2. Description of Prior Art:
The conventional oxygenators are broadly grouped under two types, the bubble type and the membrane type. Recently, the oxygenators of the membrane type which have a less adverse effect on the blood than those of the bubble type have come to find more popular utility. The membrane type oxygenators operate on the principle that exchange of oxygen gas for carbon dioxide gas in blood is effected through the medium of a gas-exchange membrane such as, for example, a membrane made of porous synthetic resin when the oxygen gas is supplied to one side and the blood to the other side respectively of the gas-exchange membrane.
The oxygenators of this type, however, have the drawback that their gas-exchange capacity is gradually degraded after protracted use. To be more specific, this degradation of the gas-exchange capacity proceeds as the water in the blood permeates the membrane, leaks into the oxygen gas, and transforms into steam, this steam is condensed into water drops on exposure to a cool ambient air, and the water drops wet the surface of the membrane. This phenomenon is called a "wet lung."
For the purpose of enabling the water drops adhering to the surface of the membrane to fall down easily, it has been proposed to change the shape of the housing for the oxygenator or to change the material for the membrane. The improvements so proposed, however, do not overcome the drawback perfectly.
An object of this invention, therefore, is to provide a novel oxygenator for blood.
Another object of this invention is to provide an oxygenator so improved as to mitigate notably the loss of the gas-exchange capacity by aging.